A known automatic warehouse for a clean room comprises a pair of racks and a stacker crane automatically running along a running path arranged between the racks. The stacker crane comprises a mast extended vertically from a lower frame and a platform that can elevate and lower along the mast. The stacker crane also has running means and a loading mechanism.
In this stacker crane, the mast, which supports the platform, is configured to extend in a vertical direction. Accordingly, if the mast has an insufficient rigidity, it may be swung in the running direction during running or when the running operation is stopped. To hinder this swing, the frame structure of the stacker crane including the mast must have an increased rigidity. However, increasing the rigidity requires the thickness of the mast to be increased, thus increasing the size of the stacker crane.
Further, an automatic warehouse provided with a stacker crane uses electric power as a drive source. Accordingly, if trouble such as electric power interruption occurs, the stacker crane cannot be operated until electric conduction is resumed. Thus, even if works in process that must be processed urgently are stocked in the automatic warehouse, the urgent works in process cannot be retrieved until the trouble is settled to allow the stacker crane to be restarted.
It is thus an object of the present invention to provide a stacker crane having a frame structure that has an increased rigidity in spite of its compact configuration, the stacker crane allowing articles stocked in an automatic warehouse to be retrieved even if electric power interruption or a failure occurs.